| Abstrakt: |
In the middle of the São Francisco Basin, the sub-basins of Indaiá and Borrachudo stand as attractive unconventional gas plays. However, the high complexity of developing unconventional reservoirs raises many issues concerning the environmental sustainability of this enterprise. In this context, a pre-operational assessment of the groundwater vulnerability is crucial to compound a robust environmental baseline for the shale gas industry. The present study assesses the groundwater's intrinsic and specific vulnerability of the Indaiá and Borrachudo basins as a part of an environmental baseline study for further shale gas exploration. GOD index method (an overlay and index geoprocessing technique) was applied to assess the aquifer's intrinsic susceptibility regarding the groundwater confinement (G), the overlying strata (O), and the depth of the groundwater table (D). The specific vulnerability assessment considered the intrinsic vulnerability and the land cover/use of the area, concerning the diversity and the toxicity of pollutants inherent to each anthropogenic activity. The results indicate that 52.69%, 25.12%, and 17.57% of the aquifer area have medium, high, and extreme intrinsic vulnerability, respectively. Medium, high, and extreme specific vulnerability occur, respectively, in 14.37%, 0.28%, and 17.10% of the total area. Specific vulnerability assessment suggests an overall vulnerability reduction due to the basin's low levels of anthropogenic pressures. Three gas wells overlay moderate intrinsic vulnerability, and one well is above the high vulnerability area. Findings from this research are helpful to design strategies and actions aimed to protect groundwater systems and guarantee an unconventional gas development grounded in environmental principles in Brazil. [ABSTRACT FROM AUTHOR] |
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